How to Maintain and Repair FRP Tanks and Pipes
How to Maintain and Repair FRP Tanks and Pipes
FRP tanks, known as Fiberglass Reinforced Tanks, are high-strength, cost-effective, lightweight, reliable, strong, and highly corrosion-resistant. They can also withstand high-temperature chemicals, which makes them ideal for chemical processing. As a cost-effective investment, they are a top choice for the industrial industry, from pulp and paper mills to chemical plants.
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Understanding the tips and tricks for maintaining and repairing FRP tanks and Pipes can make the difference between a tank lasting 5-10 years to 30+. Fiberglass Tanks are composite materials of varying thicknesses (Resin / Epoxy-Resin, Fiberglass Mat, Wax coating, etc.
What causes areas of failure in
FRP Tanks
?
FRP Tank Filament Wound Air pockets are the enemy of the FRP Tank manufacturing process. If not rolled out properly, air can become trapped and lead to a partially filled or empty space, e.g., voids, in the finished laminate. Voids lead to leaks and cracks that need to be repaired.
Voids can be caused by the viscosity of the resin (i.e., the thickness of liquids), poor mixing process, inaccurate cure temperature, and insufficient reinforcement compaction to remove their air bubbles before curing.
FRP Tanks can lose their hardness, stiffness, and toughness from one air pocket, but we can easily repair these defects.
How can I prevent UV Damage to my FRP Tank?
FRP structures exposed to extended periods of ultraviolet light can not only cause the structure to fade but expose the fibers and corrode the FRP's ability to resist chemicals. This is known as Fiber Blooming.
As time passes, the resin breaks down and exposes the glass fibers within. As a result, the surface texture changes and reduces chemical resistance.
You can prevent UV damage by applying a UV-resistant gel coat to protect the structure from damaging rays. If the tank is located inside a building, a gel coat may not be necessary, but if the Tank is exposed to UV through windows, a gel coat may be required.
How do I respond to a lining failure inside my FRP Tank?
Over time, chemicals stored inside the fiber-reinforced tank will corrode wax layer (a protective coating for additional chemical resistance) and eventually cause the inner lining to fail. The inner lining can bubble, crack, shrink, delaminate, and scratch. These areas of failure will need to be ground down and patched. In many cases, a full reline of the tank will be necessary.
FRP Tank Crack ExampleWant more information on GFRP Piping? Feel free to contact us.
These tank failures will allow the chemicals to permeate the corrosion barrier into the structure of the tank or pipe and lead to leaking. This is why secondary containment is critical when dealing with harsh chemicals. Furthermore, high temperatures can cause the laminate to soften and lose its rigidity, thus becoming prone to erosion and damage, which will break down over time.
Before performing a tank reline, it's vital to assess the following: - What chemical is being stored inside the tank?
- What temperature will the tanks be stored at?
- Have I emptied the tank of its contents and cleaned it in preparation for inspection and repair work?
- Have I performed an adhesion or pull test with my materials to ensure a proper bond?
After answering these questions, the tank will need to have the damaged material removed, the surface sanded and ground, application of the glass reinforcement and resin, followed by a post-cure wax coating.
Extending the Life of
FRP Tanks
and Pipes
Fiberglass Tanks and Piping are low-maintenance and dependable solutions, but they do require maintenance. Identifying and repairing early failures and help avoid spills, leaks, and structural failures.
Our suggestion is to perform routine maintenance to maximize performance. What should you look for when inspecting a Fiberglass Tank?
Extensive cracking or crazing
Lack of "shine" on Fiberglass (e.g., losing wax coating)
Cracks and leaks around flanges and metal supports/hangers
Buildup of crystals
Discoloration in Fiberglass lining
Excessive wear on flanges
Blistering or bubbles on pipes or tank surfaces
Joints or elbows that are discolored or cracked
Don't know much about Fiberglass Tank and Pipe Repair? We can help. Our project leaders will happily provide an inspection and a free, no-obligation quote for your fiberglass tank or piping.
Request an inspection or free quote by calling 410-737- or emailing us at . For more information about Fiberglass Tank Repair, CLICK HERE. For more information about Fiberglass Piping Repair, CLICK HERE. For a no obligation free quote, CLICK HERE or visit https://www.plastechservices.com/quote
FRP Piping System Design
Regardless of the level of analysis of the piping system, the primary goal of the task is to ensure the piping has enough supports to safely carry the weight loads and other 'primary' loads, while at the same time providing sufficient flexibility to ensure the 'displacement' loads do not become unmanageable. Primary loads are those such as pressure, weight, wind, and seismic loads, and they give rise to 'primary stresses' in the piping. Primary stresses are those that are required within the piping to balance the applied primary loads. They are characterized by being able to cause ultimate failure of the piping system should they become too large.
Displacement loads are those caused by constraint of displacement of the piping such as restriction of thermal expansion or by settlement of a support or connected equipment. Displacement loads give rise to displacement stresses. Displacement stresses typically result in excessive distortion should they become too large, but they don't usually result in ultimate failure. In fact, in ductile piping systems, displacement stresses are permitted to exceed the yield strength of the material, and they are then relieved by local yielding. Due to the fact that the displacement associated with these loads is typically limited to the extent that the piping tries to expand or contract, these stresses are often referred to as 'self-limiting'.
Perhaps the most important difference between analysis of metallic piping systems and FRP piping systems is in the way that displacement stresses are handled. In metallic piping systems, these stresses are permitted to be much higher than primary stresses. This is in recognition of the ability of the ductile material to locally yield without inducing ultimate failure. The ASME B31.1 and B31.3 piping codes treat displacement stresses as 'Expansion' stresses, and they permit the Expansion stresses (or more correctly, the expansion stress range) to be as much as 2.5 times the allowable stress for primary loads. The expansion stress range is the stress induced in the piping during a change in temperature from the highest temperature to which the piping will be exposed to the lowest temperature.
This same treatment for expansion stresses is not appropriate for FRP piping. FRP does not display significant ductile behavior, so expansion stresses should be treated essentially the same as primary stresses. This fact has given rise to the practice of analyzing FRP piping systems for 'Operating' loads, i.e. the combined effects of pressure, weight, and thermal loads, and comparing the resulting stresses to the allowable stress for sustained loads. In this case, the thermal stresses are calculated for the change in temperature from the minimum installation temperature to the highest temperature the system will be exposed to, and in some cases, from the maximum installation temperature to the lowest temperature.
ASME NM.21 permits slightly higher stresses in load cases that include displacement loads, but this is only 10%, much less than is permitted for metallic piping systems.
In our next article we'll take a look at what information is required to conduct a pipe stress analysis, and in particular, where the allowable stresses for FRP piping come from.
1ASME NM.2 'Glass-Fiber-Reinforced Thermosetting-Resin Piping Systems
Previous article in the series: Pressure Design of FRP Piping Components ' Flanges
Next in the series: Elastic Properties for FRP Pipe Stress Analysis
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